On Wikipedia they mention "Volvo WhiteGMC" as make, but we could indeed use "WhiteGMC" rather than "White/GMC".

Volvo WhiteGMC was never used as make, I'm afraid that the WP page is another one written without checking...
But as the brochures show indeed Volvo and WhiteGMC together (but usually with WhiteGMC at first, see the pictures in the previous post), this could explain the mistake...

The accurate company name was Volvo GM Heavy Truck Corparation, and the 2 makes sold by it were Volvo and WhiteGMC:

Only 2 cars were concerned, so I corrected them: the Porsche 718 (2016+718 Boxster / 2017+ 718 Cayman), even if mainly facelifted versions of the former 981 models, have the 982 factory code.
Lot of websites and several Wikipedia pages already identify them that way (en, de, it, sv...) and, above all, Porsche's corporate site does it so too (de, fr).